This invention generally relates to systems for cleaning articles by means of volatile solvents, and is specifically concerned with a closed loop system and method for cleaning contaminated articles with fluorocarbon solvents such as Freon* without releasing any of the fluorocarbon solvent into the atmosphere. * Freon is a registered United States Trademark owned by the I.E. DuPont DeNemours and Company located in Wilimington, Del.
Apparatuses for cleaning articles by means of volatile fluorocarbon cleaning solvents are known in the prior art. Such devices are often used to clean tools and garments used by the maintenance personnel in nuclear power facilities which have become contaminated with radioactive particles. These devices typically include a "glove box" type cleaning chamber that has rubber gloves mounted onto a plexiglass plate so that a worker may slide his hands through the gloves and manipulate and observe the article to be cleaned within the cleaning chamber. A solvent nozzle is included within the cleaning chamber for discharging a high velocity jet of a volatile cleaning solvent, such as Freon 113, against the article to be cleaned and decontaminated. Many of these devices include some sort of solvent formation system that liquifies the solvent vaporized by the solvent nozzle, and collects the solvent in a solvent sump located beneath the cleaning chamber. Some of these devices include a solvent distillation system which boils the used solvent in order to separate it from the particle contaminates and dirt that has become entrained within it, and then condenses the vapors of the distilled solvent back into a liquid solvent which is circulated back to a solvent reservoir connected to the solvent nozzle.
While many of the solvent cleaning devices of the prior art are effective in both decontaminating and cleaning a contaminated and soiled article, and are further capable of reclaiming and recirculating a substantial portion of the Freon 113 or other volatile cleaning solvent they employ, none of these systems is 100 percent effective in preventing the discharge of some Freon or other fluorocarbon solvent into the atmosphere. This is a particularly serious shortcoming, since it is now widely recognized that the discharge of such fluorocarbon solvents into the atmosphere tends to undermine the effectiveness of the ionosphere in shielding the earth from harmful ultraviolet radiation. The threat posed to the ionosphere by such vaporized fluorocarbons has recently induced national sanctions in the form of U.S. Environmental Protection Agency regulations mandating a staged reduction in the use of such fluorocarbons beginning in 1989, as well as international sanctions in the form of the Montreal Protocol of 1988 which likewise calls for reduced usage of volatile fluorocarbons by all industrialized nations commencing in 1989. While there are some prior art cleaning devices that purport to prevent all fluorocarbons from escaping into the atmosphere, the applicants have observed that significant amounts of fluorocarbons do in fact escape from these devices. The most common area of escape observed by the applicants is in the area of the solvent drain and sump. When the door of the cleaning chamber of these systems is opened, there is often a direct interface between the ambient atmosphere and the surface of the liquid Freon which has been collected in the sump at the bottom of the cleaning chamber. Some prior art devices have attempted to eliminate this interface with a pivoting barrier that operates somewhat like a flap valve. However, vapor pressure exerted by the solvent at ambient temperatures can cause some vaporized solvent to leak through such barriers and flow into the atmosphere. The second area of escape is the vent outlets which are present in all prior art devices of which the applicants are aware. Such vent outlets are necessary at various points in such prior art devices in order to avoid build ups of localized pressure which could either render the solvent reclamation system ineffective or possibly rupture the gloves mounted in the glove box of the cleaning chamber. While some of these prior art devices have attempted to address the problem of solvent escape by providing HEPA filters over their vent outlets, the applicants have observed that significant amounts of fluorocarbon solvent escape through these filters.
Clearly, there is a need for a cleaning device having a closed loop system for cleaning articles with volatile cleaning solvents which completely prevents any escape of the solvents into the ambient atmosphere. Ideally, such a system should be at least as effective in cleaning contaminated or soiled articles as prior art solvent cleaning systems, and in reclaiming and recycling cleaning solvents for continuous reuse. Finally, such a system should be safe, reliable, and afford a maximum amount of cleaning in a minimum amount of time.